Development of the intestinal mucosal barrier

Author:Walker AW|Journal:Journal of Paediatric Gastroenterology

Volume: 34

Issue: Supplement 1

DOI:10.1097/01.MPG.0000017295.92960.78
This review will cover important landmarks in our understanding of mucosal barrier function. Initially, the epithelial lining of the intestinal surface was considered simply a physical barrier to foreign antigens and microorganisms in the intestinal lumen. Subsequently, several seminal observations suggested that the gut epithelium was an active participant in the mucosal immune response and provided communication between luminal stimulants and underlying lymphoid elements in the lamina propria. In response to interaction with microbes in the lumen, the epithelium can regulate the transcription of inflammatory cytokines for excretion into the lumen and interstitium and can up-regulate surface molecules, such as class-II antigens and the polymeric immunoglobulin-A (poly-IgA) receptor, for control in handling foreign antigens. This interaction with luminal pathogens and commensal flora with the gut is termed microbial–epithelial “cross talk” and represents an important contributor to intestinal barrier function. Finally, we have evidence that components of the intestinal mucosal barrier are underdeveloped at birth and respond inappropriately to luminal stimuli. As a result of this immature, inappropriate response to microbial stimuli, certain infectious diseases occur in greater frequency during infancy.